Formerly in China, the zi would replace a male's given name when he turned twenty, as a symbol of adulthood and respect.[citation needed] It could be given either by the parents or by the first personal teacher on the first day of family school. Females might substitute their given name for a zi upon marriage. One also may adopt a self-chosen courtesy name.

A courtesy name is not to be confused with an art name (hào, Chinese: 號, Korean: 호), another frequently mentioned term for an alternative name in Asian culture-based context. An art name is usually associated with art and is more of a literary name or a pseudonym that is more spontaneous, compared to a courtesy name.

Compare this usage with the Roman practice of supplying a Cognomen like the name Caesar which originally may have only designated someone with a thick head of hair.

The zì, sometimes called the biǎozì（表字）or "courtesy name", is a name traditionally given to Chinese males at the age of 20, marking their coming of age. It was sometimes given to females upon marriage. The practice is no longer common in modern Chinese society. According to the Book of Rites, after a man reaches adulthood, it is disrespectful for others of the same generation to address him by his given name, or míng. Thus, the given name was reserved for oneself and one's elders, while the zì would be used by adults of the same generation to refer to one another on formal occasions or in writing; hence the term "courtesy name".

The zì is mostly disyllabic, consisting of two Chinese characters, and is usually based on the meaning of the míng or given name. Yan Zhitui of the Northern Qi dynasty believed that while the purpose of the míng was to distinguish one person from another, he asserted that the zì should express the bearer's moral integrity.

The relation which often exists between a person's zì and míng may be seen in the case of Chiang Kai-shek (蔣介石), whose ming was Zhōngzhèng (中正，Romanized as Chung-cheng) and zi was Jieshi (介石，Romanized as Kai-shek). Thus he was also called 蔣中正 (Chiang Chung-cheng) in some context.[clarification needed]

Another way to form a zì is to use the homophonic character zǐ (子) – a respectful title for a male – as the first character of the disyllabic zì. Thus, for example, Gongsun Qiao's zì was Zǐchǎn (子產), and Du Fu's: Zǐměi (子美).

It is also common to construct a zì by using as the first character one which expresses the bearer's birth order among male siblings in his family. Thus Confucius, whose name was Kǒng Qiū (孔丘), was given the zì Zhòngní (仲尼), where the first character zhòng indicates that he was the second son born into his family. The characters commonly used are bó (伯) for the first, zhòng (仲) for the second, shū (叔) for the third, and jì (季) typically for the youngest, if the family consists of more than three sons. General Sun Jian's four sons, for instance, were Sun Ce (伯符, Bófú), Sun Quan (仲謀, Zhòngmóu), Sun Yi (叔弼, Shūbì) and Sun Kuang (季佐, Jìzuǒ).

The use of zì began during the Shang dynasty, and slowly developed into a system which became most widespread during the succeeding Zhou dynasty. During this period, women were also given zì. The zì given to a woman was generally composed of a character indicating her birth order among female siblings and her surname. For example, Mèng Jiāng (孟姜) was the eldest daughter in the Jiāng family.

^Tianjun Liu, Xiao Mei Qiang (2013). Chinese Medical Qigong. p. 590. ISBN1848190964. Mencius (371—289 BCE), born in Zou county (Shandong province), first name Ke, style name Zi Yu, was a famous philosopher, educator, politician, and expert on the Qigong life nurturing of Confucius in the Zhanguo Period.

^Origins of Chinese Names. 2007. p. 142. ISBN9812294627. In ancient times, besides having a surname and a given name, one would have a courtesy name "Zì" as well. The courtesy name was the proper form of address for an adult. On reaching 20 years of age, young men would "put on the hat" as ...